Avoid 100% CPU on asyncio.sleep(0)

[higucheese]

When I used vpython on jupyter notebook, I faced a problem that a vpython kernel running on a remote server kept using 100% CPU. After surveying, I found the CPU spin was caused by asyncio.sleep(0) function. This issue ( python/asyncio#398 ) describes the problem in detail.

To solve the problem, simply waiting longer than zero works well; the CPU usage changes from 100% to 1%. Of course, this change does not harm the performance of vpython in my sense.

[mwcraig]

@higucheese -- thanks so much for the pull request! Just one extra thing to do before we merge: please add yourself to the list of contributors here https://github.com/vpython/vpython-jupyter/blob/master/CONTRIBUTORS.md

If you would like me to take care of that for you just let me know.

[higucheese]

@mwcraig -- thank you for replying to this PR.
There is no problem with adding myself to the list. But how should I do that? Would you be able to add '@higucheese' to the list?

[mwcraig]

@higucheese -- yep, I can add it. What would you like us to list as your name (if anything) in addition to your github username?

[higucheese]

Would you add 'Tomokazu Higuchi (@higucheese)' to the list like other additional contributors? Thank you!

[mwcraig]

Thanks again @higucheese, merging!